Wear of ceramic and titanium ball attachments in subjects with an implant-retained overdenture: a controlled clinical trial

Novel PEEK Retentive Elements versus Conventional Retentive Elements in Mandibular Overdentures: A Randomized Controlled Trial

Background. Many patients suffer from lack of retention of conventional mandibular overdentures due to loss of clip retention over time. Computer-aided design-computer-aided manufacturing (CAD-CAM) milled polyether ether ketone (PEEK) materials may be used for the construction of retentive housing and clips for improving retention of implant-supported overdentures. Objective. To compare retention and patient satisfaction of implant-supported mandibular overdentures retained by conventional nylon clip and metal housings for ball attachments versus PEEK clip and housings. Methods. Twenty-two participants were divided into 2 equal groups (n = 11). The conventional group received implant-supported mandibular overdentures retained by metal housings and nylon retentive elements, while the PEEK group received implant-supported mandibular overdentures retained by PEEK retentive elements and housings. The PEEK retentive elements were made using computer-aided design and computer-aided manufacturing (CAD-CAM). The evaluation included measuring the retention by applying a gradual pulling up force by force meter and patient satisfaction with a 7-point visual analog scale (VAS) at overdenture insertion and 3, 6, and 12 months subsequently by a research interviewer. Results. The PEEK group showed statistically significantly increased retention force ( $P<0.05$ ) at the time of insertion (37.6/17.79) and after 3 months (33.9/16.78), 6 months (32.7/15.97), and 12 months (31.65/13.05). The conventional group had a statistically significantly higher mean overall satisfaction ( $P<0.05$ ) at the time of insertion (65/82.18). No statistically significant difference was found after 3 months (87.81/84.72). The PEEK group showed statistically significantly higher mean overall satisfaction ( $P<0.05$ ) after 6 months (86.36/80.18) and 12 months (85.45/79.54). Conclusions. According to the results of this study, the PEEK retentive material provided more retention than did the conventional material and led to improved patient satisfaction. The study was registered at clinical trials.gov (https://clinicaltrials.gov/ct2/show/NCT05079048).

Attachment-Retained Unilateral Partial Denture versus Tooth Implant-Supported Prosthesis in Mandibular Distal Extension Cases: A Randomized Controlled Trial

Objective:

To evaluate patients’ satisfaction, biting force measurement, and radiographic evaluation of abutment teeth of tooth implant-supported fixed partial denture, unilateral attachment, and conventional partial denture in mandibular distal extension cases.

Materials and Methods:

Twenty-four participants were selected according to the following criteria: participants with unilateral mandibular distal extension with last standing second premolar abutment; participants having abutments with sufficient occluso-gingival height and good periodontal condition. Participants were divided into the following three equal groups: participants of the implant group received fixed tooth implant-supported fixed partial dentures, attachment group participants received unilateral attachment removable partial dentures, and conventional group participants received conventional removable partial dentures. The evaluation included patient satisfaction using “OHIP14” questionnaires, biting force measurement, and radiographic evaluation of terminal abutments using the ANOVA test.

Results:

Participants of the implant group were mainly satisfied with their prosthesis than the attachment group, which is higher than the conventional. Regarding biting force measurement, there is a statistically significant difference (p < 0.05) between all groups, including the implant group and attachment group, as well as between attachment and conventional group (p < 0.05). The conventional group showed statistically significant (p < 0.05) highest mean bone loss, while there was no statistically significant difference between implant and attachment groups; both showed statistically significantly lower mean amounts of bone loss.

Conclusion:

The tooth implant-supported fixed prosthesis could be considered a superior line of treatment for managing distal extension cases. Unilateral attachment, which is considered an excellent alternative in the case of implant placement, is not recommended.

Effect of specific retention biomaterials for ball attachment on the biomechanical response of single implant-supported overdenture: A finite element analysis

PURPOSE

The purpose of this finite element analysis (FEA) was to evaluate the effect of specific retention biomaterials with different elastic modulus on the biomechanical response to the axial and off-axial biting loads of a mandibular midline single implant-supported overdenture (SIO) model.

METHODS

Five 3-dimensional (3D) finite element models of an edentulous mandible with SIO were designed as follows: model M with a titanium retentive element for ball attachment, model P with a PEEK retentive element, model S with a silicone resilient liner retentive element, model T with a thermoplastic acrylic resin retentive element made from a CAD-CAM material, and model A with a polyacetal resin retentive element. Posterior bilateral vertical load (PV) at the 1st molar areas and anterior oblique load (AO) at the incisal edge of the mandibular central incisors at a 30-degree angle of 100 N were applied. Stress values were recorded.

RESULTS

Stress values were higher for all models under (AO) loading than under (PV) loading. Model M recorded the highest stress values on the implant, its components, cortical, and cancellous bone under both loading conditions. Under (AO) loading condition, the ball abutment von Mises stress value in model S was almost 7 times lower than that of model M (19 and 130 MPa respectively) and the other 3 models (P, T, and A) (119, 121, and 120 MPa respectively). However, model S recorded the highest value of denture base stress at the attachment area.

CONCLUSIONS

The elastic modulus of retention materials can affect stresses generated on the implant overdenture components and supporting structures.

Evaluation of changes in mechanical properties of O-ring in one-piece and two-piece ball retained implant-supported overdentures: A three-year retrospective study

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

Nanotribological response of a-C:H coated metallic biomaterials: the cases of stainless steel, titanium, and niobium

Background Wear and corrosion have been identified as two of the major forms of medical implant failures. This study aims to improve the surface, protective and tribological characteristics of bare metals used for medical implants, so as to improve scratch resistance and increase lifetime. Methods Hydrogenated amorphous carbon (a-C:H) films were deposited, using plasma enhanced chemical vapor deposition (PECVD), on stainless steel (SS), titanium (Ti) and niobium (Nb) metal plates. Nanomechanical and nanotribological responses were investigated before and after a-C:H deposition. Film thickness and density were quantified through X-ray reflectivity, and surface morphology before and after deposition were measured using atomic force microscopy, whereas the tribomechanical characteristics were probed using instrumented indentation. Results and conclusions Films of approximately 40 nm in thickness and density of 1.7 g/cm³ were deposited. The a-C:H films reduce the roughness and coefficient of friction while improving the tribomechanical response compared with bare metals for Ti, SS and Nb plates. The very good tribomechanical properties of a-C:H make it a promising candidate material for protective coating on metallic implants.

Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics

This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.

A technique for relining bar-retained overdentures

This article describes a technique for relining a mandibular bar-retained overdenture that allows recording the soft tissue beneath the bar and makes it possible to replace or modify the retentive bar attachment simultaneously with the reline procedure.